The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to produce pulse width modulated (PWM) power supply controllers. In some applications, it was important to control the maximum power that was delivered by a power supply system to a load. Some prior PWM controllers provided for adjusting the maximum duty cycle of a drive signal that was produced by the PWM controller. However, these prior PWM controllers did not accurately limit the maximum power delivered to load. One example of such a prior PWM controller is disclosed and U.S. Pat. No. 6,304,462 that issued to Balakrishnan et al on Oct. 16, 2001.
In other applications, it was important to set the frequency of the drive signal. However, the prior PWM controllers did not accurately set the frequency.
Accordingly, it is desirable to have a PWM controller that accurately limits the maximum power delivered to load, that can set the duty cycle of the PWM drive signal to limit the maximum power delivered to the load, and that can accurately set the frequency of the drive signal without affecting the duty cycle.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor or a cathode or anode of a diode, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as certain N-channel or P-Channel devices, a person of ordinary skill in the art will appreciate that complementary devices are also possible in accordance with the present invention. It will be appreciated by those skilled in the art that the words during, while, and when as used herein are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action.